Field of the Invention
The present invention relates to a gas sensor including a detecting element for detecting a specific gas contained in an object measurement gas.
Description of the Related Art
In the related art, for example, gas sensors including a detecting element for detecting a specific gas, such as oxygen, which is contained in an object measurement gas, such as exhaust gas, are widely known.
In this type of gas sensor, in addition to the detecting element, a metal shell that allows a front end portion and a rear end portion of the detecting element to protrude therefrom and surrounds the periphery of the detecting element, a terminal metal fixture that abuts onto the rear end portion of the detecting element, and a tubular separator with insulating properties that accommodates the rear end portion of the detecting element or the terminal metal fixture, and the like are provided.
Among these, for example, a plate-shaped laminated type oxygen sensor element in which a plurality of ceramic layers or the like are laminated is known, as the detecting element, as described in JP-A-2007-163272. In detail, this detecting element includes a detecting portion or a heater at a front end portion exposed to an object measurement gas, such as exhaust gas. Further, electrode pads are connected to lead wires that extend from the detecting portion or the heater, on the outer surface of the rear end portion, and the terminal metal fixture is adapted to abut the electrode pads.
Incidentally, in the above-described related art, as shown in FIG. 11A, C chamfering is performed on a rear end portion P2 of a detecting element P1 to provide a C chamfered portion P3. This is because, when the rear end portion P2 of the plate-shaped detecting element P1 is inserted into a separator P5 (refer to FIG. 11B), the C chamfered portion P3 is easily inserted to follow a through hole P6 of the separator P5. Further, there is a possibility that a corner portion P7 of the rear end portion P2 may come into contact with an opening of the through hole P6 of the separator P5. Further, chipping may occur at the corner portion P7 of the rear end portion P2 of the detecting element P1.
In addition, the corner portion P7 is a portion where a ridgeline P11 formed by a principal surface P8 and a side surface P9, a ridgeline P12 formed by the principal surface P8 and a rear end surface P10, and a ridgeline P13 formed by a side surface P9 and the rear end surface P10 are combined.
However, in a case where a gas sensor is manufactured, as shown in FIG. 11B, the detecting element P1 is inserted at an incline with respect to the separator P5 and not coaxially with the separator P5. In that case, there is a problem in that a corner portion P14 of the rear end portion P2 of the detecting element P1 may strike the opening of the through hole P6 of the separator P5 or the inner surface of the separator P5, and chipping may occur in the detecting element P1.
In addition, the corner portion P14 is a portion where the ridgeline P11 formed by the principal surface P8 and the side surface P9, a ridgeline P15 formed by the principal surface P8 and the C chamfered portion P3, and a ridgeline P16 formed by the side surface P9 and the C chamfered portion P3 are combined.
That is, even if the rear end portion P2 of the detecting element P1 is provided with the C chamfered portion P3 in order to improve the insertion performance of the detecting element P1 into the separator P5 and prevent chipping of the corner portion P7, there is a problem in that the occurrence of chipping in the corner portion P14 of the detecting element P1 cannot be sufficiently suppressed by providing the C chamfered portion P3 alone.